Arsenotučekite

Chemical formula: Ni₁₈Sb₃AsS₁₆

Arsenotučekite is a rare nickel, antimony, and arsenic sulfide, forming microscopic, metallic grains in serpentinites.

## Characteristics Arsenotučekite is a very rare mineral from the sulfide group. It occurs as extremely small, anhedral (irregularly shaped) grains, usually not exceeding several tens of micrometers in size. It is observed in polished sections under a microscope, where it forms inclusions within other minerals. Its identification requires advanced analytical techniques. ## Physical Properties This mineral is characterized by a metallic luster. Due to the microscopic size of its grains, most of its physical properties, such as hardness, density, fracture, or cleavage, have not been precisely determined. ## Colors and Varieties In reflected light (under a microscope), arsenotučekite is cream-white with a pinkish tint. No varieties have been distinguished. ## History and Name The mineral's name refers to its chemical composition – the presence of arsenic – and honors Karel Tuček (1900-1984), former curator of the mineralogical collection at the National Museum in Prague (Czech Republic). It was approved as a new mineral by the IMA in 1978. ## Applications Arsenotučekite has no practical applications. It is of purely scientific significance and is an object of interest for specialized collectors of microscopic minerals.

Properties

Luster: Metallic
Transparency: Opaque
Crystal system: Tetragonal

Diagnostic features

## Identification Macroscopic identification of arsenotučekite is impossible. Identification requires analysis in reflected light under a polarizing microscope and confirmation of chemical composition using an electron microprobe (EDS/WDS). In reflected light, it exhibits weak anisotropy. ## Distinguishing from Similar Minerals Under a microscope, it can be confused with other rare nickel sulfides, such as tučekite, hauchecornite, or pentlandite. Definitive differentiation is only possible based on chemical analysis, which will reveal the presence and proportions of nickel, antimony, arsenic, and sulfur. ## Crystal Forms Arsenotučekite forms exclusively microscopic, anhedral (irregular) grains and aggregates. No well-formed crystals have been observed.

Geological environment

## Genesis Arsenotučekite forms as a result of hydrothermal processes within serpentinized ultramafic rocks (serpentinites). It crystallizes at relatively low temperatures, forming in small fissures and rock cavities. ## Mineral Associations This mineral co-occurs with other nickel sulfides and arsenides. It is most commonly associated with tučekite, maucherite, nickeline, pentlandite, heazlewoodite, as well as chromite, magnetite, and minerals from the serpentine group. ## Localities The only confirmed occurrences of arsenotučekite worldwide are the type locality in Dobszyńce (Dúbrava) near Rožňava in Slovakia, and a nickel ore deposit near the town of Almalyk in Uzbekistan.

Rarity

Very rare

For collectors

## Quality Criteria As a microscopic mineral, arsenotučekite is not evaluated according to typical criteria such as crystal size or form. The collector's value of a specimen depends on the abundance of arsenotučekite grains on the rock matrix and the presence of well-defined associated minerals. Samples from the type locality, with analytically confirmed mineral occurrence, are the most valuable. ## Popular Localities The only source of specimens available on the collector's market is its type locality – Dobszyńce in Slovakia.

Care and storage

## Cleaning Specimens containing arsenotučekite, which are typically rock fragments, should only be cleaned with compressed air to remove dust. Any "wet" cleaning methods are discouraged as they can damage both the mineral itself and associated minerals. ## What to Avoid Avoid contact with chemicals, acids, and detergents. Changes in temperature and humidity can be detrimental to the entire rock matrix. Do not subject the specimen to ultrasonic cleaning. ## Storage Microscopic specimens, such as those with arsenotučekite, are best stored in specialized "micromount" boxes, which protect them from dust, mechanical damage, and sudden environmental changes.

Sources

IMA Mineral List (CNMNC)